Studies are planned of phagocytic and non-phagocytic functions of (especially polymorphonuclear) leukocytes, that bear on aspects of the acute inflammatory response. The research plan is particularly aimed at the relationships among specific but overlapping areas of leukocyte activity: particle ingestion per se, the increased metabolic activity that ordinarily accompanies phagocytosis, degranulation of lysosomal structures in leukocytes, and intracellular killing. The ways in which these activities can be separated from one another may distinguish obligate interactions from mere concomitance, and may reveal the specific pathways by which cell function is altered. The experimental approach will be through various agents and situations in which one or more of these activities appear to be altered, including 1) leukocytes treated with bacterial endotoxin, with hormones, with agents designed to alter intracellular levels of cyclic nucleotides, with abnormal serum (as from renal transplant patients), and with urate in solution, 2) leukocytes from patients with chronic granulomatous disease of childhood, and 3) leukocytes treated with substances that produce ultrastructural alterations in fibrillar elements, such as the metaphase-arresting agents, colchicine, vinblastine, and griseofulvin (affecting microtubules), and cytochalasin B (affecting microfilaments). From the viewpoint of comparative cell function, certain of the last group of substances are also considered as they affect the movement of melanin granules in melanocytes, the organization of the mitotic spindle in dividing cells, and the receptivity of vascular endothelium for marginating granulocytes.